Default component used in install() commands.
If an install() command is used without the COMPONENT argument, these files will be grouped into a default component. The name of this default install component will be taken from this variable. It defaults to Unspecified.
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© 2000–2011 Insight Software Consortium
Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.7/variable/CMAKE_INSTALL_DEFAULT_COMPONENT_NAME.html